Polysaccharide compositions

ABSTRACT

Polysaccharides are at least partially hydrolyzed by contact with a composition containing urea, sulfuric acid, and water in which the urea/sulfuric acid molar ratio is less than 2. Such proportions of urea and sulfuric acid assure the presence of the monourea adduct of sulfuric acid. The polysaccharide can be hydrolyzed to an extent sufficient only to hydrate the polysaccharide to produce a hydrated polysaccharide such as hydrated cellulose, or it can be completely hydrolyzed to its constituent monosaccharides. Thus, cellulose can be converted to glucose.

RELATED APPLICATIONS

This application is a division of my co-pending application Ser. No.673,358, METHODS FOR HYDROLYZING POLYSACCHARIDES AND COMPOSITIONS USEFULTHEREIN, filed Nov. 20, 1984 now U.S. Pat. No. 4,664,717 which was acontinuation-in-part of my copending application Ser. No. 455,268,Cellulosic Composition and Methods for Treating Cellulosic Materials,filed Jan. 3, 1983; Ser. No. 455,317, Plant Seed Compositions andMethods for Treating Plant Seeds, filed Jan. 3, 1983; Ser. No. 442,296,Systemic Herbicidal Compositions and Methods for Use, filed Nov. 17,1982, now abandoned; Ser. No. 444,667, Methods for ControllingVegetation, filed Nov. 26, 1982 now abandoned; Ser. No. 453,282, Methodsfor Selectively Controlling Plant Suckers, filed Dec. 27, 1982 now U.S.Pat. No. 4,522,644; and Ser. No. 453,496, Acid-Catalyzed Reactions andCompositions for Use Therein, filed Dec. 27, 1982.

BACKGROUND

1. Field of the Invention

This invention relates to the field of polysaccharide hydrolysis and, inparticular, it relates to methods and compositions useful for thepartial hydrolysis (including hydration) of polysaccharides and to thecomplete hydrolysis of polysaccharides to form monosaccharides.

2. Description of the Art

The uses for partially and completely hydrolyzed polysaccharides aremany and various. Sugars (primarily mono- and disaccharides) are used asfoods and in foods for sweetening and food value, for the manufacture ofsyrups, confectioneries, preserves, etc.; as demulcents and lenitives;in the manufacture of soaps, pharmaceutical products, chemicalintermediates for detergents, emulsifying agents, plasticizers, resins,explosives, glues, insecticides, and other products. One use for sugars,which is of current importance, is in their conversion by chemical orenzymatic processes to alcohols which are useful as fuels and fueladditives and in the manufacture of plastics, synthetic rubber,pharmaceuticals, and other chemical products. Partially hydrolyzedpolysaccharides, including hydrated polysaccharides such as hydratedcellulose, are also useful in a variety of applications including themanufacture of glycogen, processed starch, and as chemical precursersfor the manufacture of paper, fibers (including vulcanized fibers,mercerized cotton, and viscose rayon), and others.

While millions of pounds of various sugars (principally mono- anddisaccharides such as glucose, sucrose, fructose, and maltose) areproduced annually, most lower molecular weight mono- andpolysaccharides, such as the sugars, are chemically bound into highmolecular weight polysaccharides such a carbohydrates and animal andplant starches. By far the most abundant polysaccharide is cellulosewhich is the basic building block of all vegetable matter, and which isgrown, harvested, and disposed of in immense quantities. Approximately900 million metric tons of cellulose waste (including discarded paper,crop stubbles such as corn stalks, rice stubble, etc., and sawdust) areproduced in the United States each year. An immerse quantity ofpotential energy in the form of glucose is locked into this cellulosewaste, and the great advantage to be gained by releasing that energy inthe form of glucose has not gone unnoticed.

Several methods have been suggested for hydrolyzing higher molecularweight polysaccharides, such as cellulose, to their partially orcompletely hydrolyzed subunits such as glucose, and several arepracticed commercially. For instance, it is known that polysaccharides,such as cellulose, can be hydrolyzed by the action of a strong base suchas sodium hydroxide and calcium hydroxide. However, reaction rates arevery slow, particularly at lower temperatures. Thus, economic productionof base-hydrolyzed polysaccharides requires long contact times, highcaustic concentrations (and cost) and relatively high temperatures onthe order of 300° F. (which requires the use of pressurized treatingvessels). Furthermore, base is consumed in such processes in amountsproportionate to the amount of product obtained. A variety of bacterialand enzymatic processes also is known. For instance, it is known thatpapyan enzyme, if present in sufficient quantities, will graduallyhydrolyze cellulose to glucose. It is also known that certain bacteria,such as Thermomonospora, which contain cellulase enzyme can convertcellulose to glucose for use by the bacteria, and that the cellulaseenzyme, if isolated, might be employed to obtain glucose from cellulose.It is also known that the severe hydrolysis of polysaccharides, such ascellulose, with strong mineral acids, such as sulfuric acid, can becontrolled to yield some glucose. However, dehydration and oxidationside reactions decrease the yield of glucose or other saccharide fromthe polysaccharide feed and consume the hydrolyzing agent, e.g.,sulfuric acid, as illustrated in the following expression:

    [C.sub.6 H.sub.10 O.sub.5 ].sub.n +2nH.sub.2 SO.sub.4 →n[5C+CO.sub.2 +2SO.sub.2 +7H.sub.2 O].

Accordingly, a significant need exists for improved processes forpartially or completely hydrolyzing polysaccharides to form hydratedpolysaccharides, lower molecular weight polysaccharides, and/ormonosaccharides.

It is therefore one object of this invention to provide improved methodsand compositions for hydrolyzing polysaccharides.

Another object is the provision of methods and compositions forproducing lower molecular weight polysaccharides from higher molecularweight polysaccharides.

Another object of this invention is the provision of methods andcompositions useful for converting polysaccharides to monosaccharides.

Yet another object is the provision of methods and compositions usefulfor converting cellulose to hydrated cellulose.

Another object is the provision of methods and compositions useful forconverting cellulose to glucose.

Other objects, aspects, and advantages of this invention will beapparent to one skilled in the art in view of the following disclosureand the appended claims.

SUMMARY OF THE INVENTION

Briefly, the invention provides novel methods for partially orcompletely hydrolyzing polysaccharides and compositions useful in suchmethods. More specifically, the novel methods involve contacting apolysaccharide containing 2 or more saccharide subunits with urea,sulfuric acid, and water in proportions such that the urea/sulfuric acidmolar ratio is less than 2. The polysaccharide can be partiallyhydrolyzed to form a hydrated polysaccharide such as hydrated cellulose,a lower molecular weight polysaccharide, or the correspondingmonosaccharide. The novel compositions involve combinations of one ormore polysaccharides, urea, sulfuric acid, and water, in proportionswhich correspond to a urea/sulfuric acid molar ratio less than 2. Thesecompositions optionally also can contain surfactants and/or non-aqueouspolar solvents (in addition to other components).

DETAILED DESCRIPTION OF THE INVENTION

The polysaccharides which can be treated in accordance with the methodsof this invention, and which can comprise components of the novelcompositions, include all natural and synthetic, virgin, manufactured,and/or chemically pretreated polysaccharides which contain more than 1saccharide unit per molecular. Thus, the methods of this invention canbe employed to hydrolyze all carbohydrates which contain more than onesaccharide unit per molecular including oligosaccharides, which areconventionally characterized as polysaccharides having 2 to 8saccharides units per molecular, and higher molecular weightpolysaccharides such as cellulose, rayon, vegetable starches, animalstarches (glycogen), etc.

Polysaccharides and monosaccharides make up the group of compounds knownas carbohydrates which are polyhydroxy aldehydes, polyhydroxy ketones,or compounds that can be hydrolyzed to form such compounds. Bydefinition, monosaccharides are carbohydrates which cannot be hydrolyzedto simpler compounds. As used in this disclosure, the termpolysaccharides connotes carbohydrates which can be hydrolyzed to 2 ormore monosaccharide molecules.

Monosaccharides can contain either aldehyde or keto groups; the formerbeing known as aldoses, the latter as ketoses. Glucose, produced as suchand "locked" in its hydrolyzable polymeric form--cellulose--is the mostabundant aldose. Fructose (fruit sugar) is one of the more commonketoses which is combined with glucose in the disaccharide, sucrose(common table sugar). Other common disaccharides include maltose (maltsugar), cellobiose, and lactose (milk sugar). Maltose is the majorconstituent of starch and can be obtained from starch by partialhydrolysis. Cellobiose, similarly, can be derived from cellulose such ascotton fibers by partial hydrolysis and can be further hydrolyzed toglucose. Lactose, the disaccharide of glucose and galactose, constitutesapproximately 5 weight percent of cow's milk and is obtainedcommercially from whey, a by-product of cheese manufacture. Sucrose,common table sugar, is generally obtained from sugar cane and sugarbeets and can be hydrolyzed to its constituent monosaccharides--glucoseand fructose.

Most polysaccharides are naturally occurring polymers containing one ormore different monosaccharide subunits (although synthetic forms areknown) and can be made up of hundreds or even thousands ofmonosaccharide units per molecular. The monosaccharide units in di- andhigher polysaccharides are joined through glycoside linkages which canbe broken by hydrolysis. Cellulose and plant and animal starches are byfar the most abundant polysaccharides.

Illustrative of sources of polysaccharides which can be employed in themethods and compositions of this invention are wood; paper; plant matterincluding crop foliage and stubble such as mown grass, hay, rice andcorn stubble, wood scrap, sawdust, cotton (either virgin or from scrapclothing or other textile products), vegetable scrap; and plant andanimal starches.

The polysaccharide sources employed in the methods and compositions ofthis invention can be either untreated or chemically pretreated by oneor more unrelated chemical or manufacturing processes or by processeswhich facilitate hydration such as chemical treatment to removehydrophobic substances such as lignins or to partially hydrate thepolysaccharide source. Such polysaccharide sources, if not soluble inthe urea-sulfuric acid-hydrolyzing component employed in this invention,are preferably finely divided prior to treatment or incorporation intothe compositions of this invention. Thus, finely divided materials suchas sawdust, cotton fiber, shredded paper, shredded vegetable matter,etc., are ideal polysaccharide sources. Other sources such as largerwood particles and corn stubble are preferably ground or shredded priorto treatment to increase their surface area. High surface area isparticularly preferred for polysaccharide sources which containhydrophobic components such as lignins in order to facilitate contact ofthe useful urea-sulfuric acid hydrolyzing agents with thepolysaccharide.

Lignins may optionally be removed from lignin-containing polysaccharidesources prior to hydrolysis by known chemical treatments. Lignins can beremoved from cellulosic materials by extraction with liquid ammonia orsodium ammonium bisulfite, procedures which are practiced in the paperpulp manufacturing industry. Liquid or pressurized ammonia treatmentammoniates and liquid ammonia extracts lignins from cellulose, whilesulfite treatment converts lignins to forms which are water extractable.Lignins can also be removed by the so-called Kraft process whichinvolves lignin sulfonation by reaction with sulfur dioxide followed bywater extraction.

The useful urea-sulfuric acid hydrolyzing agents are combinations ofurea, sulfuric acid, and water (in the presence or absence of othercomponents) in which the urea/sulfuric acid molar ratio is less than 2.Such proportions of urea and sulfuric acid assure that at least aportion of the sulfuric acid is present as the monourea adduct ofsulfuric acid. I have found that the monourea adduct of sulfuric acidefficiently and rapidly hydrolyzes polysaccharides in the presence ofwater. The monourea adduct is not present when the urea/sulfuric acidmolar ratio is 2 or more. In such compositions all of the sulfuric acidis present as the diurea adduct. The diurea adduct of sulfuric acid haslittle or no polysaccharidehydrolyzing activity. I have also found thatthe monourea-sulfuric acid adduct does not promote undesirable sidereactions which are characteristic of sulfuric acid-polysaccharidereactions such as sulfonation, oxidation, and dehydration. Such sidereactions unavoidably cause the loss of polysaccharide feed and sulfuricacid reagent.

Accordingly, the useful hydrolyzing components will usually haveurea/sulfuric acid molar ratios of at least about 1/4 and less than 2,generally about 1/4 to about 7/4. The more preferred compositions whichcontain less uncomplexed sulfuric acid have urea/sulfuric acid molarratios of at least about 1/2, generally about 1/2 to about 3/2. The mostpreferred hydrolyzing agents have urea/sulfuric acid molar ratios of atleast about 1/1 such that all of the sulfuric acid is complexed withurea as either the mono- or diurea adduct. It is also preferable toassure that a substantial portion of the sulfuric acid is present as themono- rather than the diurea adduct. Thus, the most preferredcompositions are those which have urea/sulfuric acid molar ratios withinthe range of about 1/1 to about 3/2.

The concentration of urea and sulfuric acid in the water-containinghydrolyzing agent should be sufficient to promote the polysaccharidehydrolysis, and I have found that catalytic amounts of urea and sulfuricacid, i.e., less than about 1 weight percent in aqueous solution, aresufficient for this purpose. However, higher urea-sulfuric acidconcentrations produce higher rates of hydrolysis and are oftenpreferred. Accordingly, the urea and sulfuric acid, in combination, willusually constitute at least about 1, generally at least about 5, andpreferably about 5 to about 99.8 weight percent of the combination ofurea, sulfuric acid, and water. The most preferred compositions arethose in which the urea and sulfuric acid, in combination, constitute atleast about 10 weight percent, usually 10 to about 99.8 weight percentof the combination of urea, sulfuric acid, and water.

Water reacts with the polysaccharide in the course of the hydrolysisreaction in amounts which appear to correspond to 1 mole of water permole of monosaccharide produced (when hydrolysis is carried completelyto the production of monosaccharides) and, accordingly, is present inthe useful hydrolyzing agents in at least minor concentrations of atleast about 0.2 weight percent. However, the useful hdyrolyzing agentscan also be very dilute, i.e., they can have a high water concentrationsof up to 99 weight percent water or more. Accordingly, waterconcentration will usually be within the range of 0.2 to about 99 weightpercent, generally about 0.2 to about 90 weight percent, and preferablyabout 5 to about 90 weight percent based on the combined weight of urea,sulfuric acid, and water.

As discussed in my copending Ser. No. 673,508, Thermally StableUrea-Sulfuric Acid Compositions and Methods of Manufacture, filed Nov.20, 1984, the disclosure of which is incorporated herein by reference,urea-sulfuric acid compositions which have less than about 1 weightpercent water are much more stable thermally than are compositions whichcontain substantially higher water concentrations. For instance,urea-sulfuric acid compositions having urea/sulfuric acid molar ratiosof about 1 which contain about 10 weight percent water have incipientdecomposition temperatures of about 176° F. (80° C.) and decomposeexplosively at about 190 to 200° F. (about 90° C.). Incipientdecomposition temperature is that temperature at which the urea-sulfuricacid component begins to decompose as indicated by effervescence (CO₂evolution) and/or discoloration of the composition, as discussed in myabove referenced copending applications. In contrast, otherwiseidentical urea-sulfuric acid compositions which contain about 1 weightpercent water or less can be heated to temperatures above 80° C. andeven above 90 or 100° C. without incipient decomposition. The advantagesof employing such low water-content compositions are evident when it isdesired to conduct the hydrolysis reaction of this invention attemperatures of 80° C. or higher.

The useful urea-sulfuric acid-water hydrolyzing agents may optionallycontain other components which do not negate the activity of thehydrolyzing agents for the hydrolysis of polysaccharides. In fact, theuse of hydrolyzing agents which contain polar solvents (other thanwater) and/or surfactants is sometimes preferred, particularly for thetreatment for polysaccharide feeds which contain hydrophobic substancessuch as lignins and/or fatty materials such as lipids. Illustrativesolvents include organic and inorganic solvents in which both urea andsulfuric acid are soluble such as dimethyl sulfoxide; alcohols, e.g.,methanol, glycol, acetone, methylethyl ketone, tetrahydrofuran;halogenated hydrocarbons such as trichloromethane and chloroform, andthe like.

One or more of such polar solvents can be present over a wide range ofconcentrations, usually within the range of about 2 to about 95 weightpercent based on the combined weight of solvent, urea, sulfuric acid,and water. Illustrative suitable surfactants are discussed in mycopending application Ser. No. 453,496 referred to above, which isincorporated herein by reference in its entirety. Surfactants can alsobe employed over a wide range of concentrations. Useful concentrationsare usually at least about 0.1 and generally about 0.1 to about 10weight percent surfactant based on the combined weight of surfactant,urea, sulfuric acid, water, and polar solvent (if present).

The useful urea-sulfuric acid-containing hydrolyzing agents can beprepared by any one of the variety of procedures. One suitable procedurefor preparing urea-sulfuric acid components which are free of thermaldecomposition products is disclosed in my application Ser. No. 318,629,Methods of Producing Concentrated Urea-Sulfuric Acid Reaction Products,filed Nov. 5, 1981, now U.S. Pat. No. 4,445,925, which is incorporatedherein by reference in its entirety. The urea-sulfuric acid componentcan also be obtained by gradually adding urea to sulfuric acid or viceversa, in the presence or absence of water and/or other solvent.Sufficient cooling must be provided to assure that the urea-sulfuricacid component does not thermally decompose. In another alternative, theurea or sulfuric acid can be added to a dispersion or solution of theother component and the polysaccharide feed material in water or othersolvent, again, with the provision that sufficient cooling is providedto prevent thermal decomposition. In this alternative, it is presentlypreferred that the urea be added to the polysaccharide dispersion orsolution before sulfuric acid is added so that the urea is present toreact with the sulfuric acid upon its addition, thereby minimizingreaction of free sulfuric acid with the polysaccharide. However, it ispresently most preferred that the urea-sulfuric acid component bepreformed prior to mixing with the polysaccharide in order to preventthe reaction of free sulfuric acid with the polysaccharide feed.

The relative proportions of urea, sulfuric acid, water, andpoloysaccharide can vary considerably depending upon the reaction rateand extent of hydrolysis desired. As mentioned previously, the urea andsulfuric acid act primarily as catalysts and are not consumed in thehydrolysis reaction (although they may be consumed by reaction withimpurities). Thus, it is necessary only that the urea and sulfuric acidbe present in catalytic amounts. However, I have found that reactionrate increases as the urea and sulfuric acid concentrations areincreased. Thus higher reaction rates can be achieved at higherurea-sulfuric acid concentrations. Accordingly, the urea and sulfuricacid, in combination, will usually be present in amounts of at leastabout 0.5, generally at least about 1, and preferably at least about 5weight percent based on the combined weight of urea, sulfuric acid,water, and polysaccharide. The majority of reaction conditions willinvolve urea-sulfuric acid concentrations within the range of about 1 toabout 90 weight percent, preferably about 5 to about 50 weight percentbased on urea, sulfuric acid, water, and polysaccharide.

Water is a reactant and is consumed in the hydrolysis reaction inproportion to the number of moles of water added to the polysaccharidefeed. For instance, the hydrolysis of one monosaccharide unit in apolysaccharide molecule to form one free monosaccharide moleculerequires the consumption of one molecule of water. Accordingly, thewater concentration employed in the hydrolysis reaction should besufficient to supply the amount of water required to effect the desireddegree of hydrolysis. All of the water either can be added initially, orit can be added incrementally during the reaction to replace waterconsumed by hydrolysis. Accordingly, the concentration of water presentin the hydrolysis reaction at any given time is generally at least about0.1 weight percent and can range up to as high as 95 weight percent ormore based on the combined weight of urea, sulfuric acid, water, andpolysaccharide. Within this range, the water concentration is generallydetermined by the desired proportion of water relative to urea andsulfuric acid which is discussed above.

Water concentration can be employed to control the rate and extent ofhydrolysis since its presence is necessary for the progress of thehydrolysis reaction. Accordingly, initial water concentrations of oneweight percent or less based on polysaccharide can be employed to assurethat no more than one weight part of water per 100 weight parts ofpolysaccharide will be added to the polysaccharide by hydrolysis. Higheror lower initial water concentrations can be employed to effect varyingdegrees of hydrolysis. Furthermore, the water concentration in thehydrolysis reaction can be maintained at a relatively low level andincrementally or continuously supplemented to maintain that level aswater is consumed in order to control the rate of hydrolysis as desired.

The polysaccharide can be contacted with the urea-sulfuric acidhydrolysis agent, and water, in the presence or absence of othercomponents, by any procedure capable of accomplishing the desired degreeof contact of these respective components. For instance, theurea-sulfuric acid component can be added to a solution or dispersion ofthe polysaccharide in water, or a water-containing urea-sulfuric acidcomponent can be sprayed onto finely divided polysaccharide-containingfeed material. In the alternative, the polysaccharide feed can beimmersed in a water-containing solution or melt of the urea-sulfuricacid component. Light misting of a polysaccharide-containing feed with awater-containing urea-sulfuric acid component can be employed to effectminor amounts of hydration on the surface of the polysaccharide feed.

The hydrolysis reaction can be conducted over a wide range oftemperatures which are sufficient to maintain the urea-sulfuricacid-water component in the form of a solution or melt and which do notexceed the thermal decomposition of the urea-sulfuric acid component.The more concentrated urea-sulfuric acid-water mixtures, i.e., those inwhich the urea and sulfuric acid, in combination, constitute 30 percentor more of the combination, will crystalize and/or will become solids attemperatures much below 0° C. The maximum temperature is preferablymaintained at a point below the incipient decomposition temperature ofthe urea-sulfuric acid component as discussed previously. Accordingly,hydrolysis temperatures will usually be at least about 0° C., generallyat least about 10° C., and preferably within the range of about 20 toabout 80° C., particularly when employing compositions which containsubstantially more than one weight percent water. As discussed above,urea-sulfuric acid components which contain about one weight percentwater or less have incipient decomposition temperatures above 80° C.Accordingly, such compositions can be employed in the hydrolysisreaction at temperatures above 80° C., or even above 100° C. or higher.

Higher reaction temperatures increase the rate of hydrolysis; thus,reaction temperature can be employed to control hydrolysis rate. Forinstance, the rate of hydrolysis of most polysaccharides in the presenceof the urea-sulfuric acid-water components is relatively low attemperatures of about 10° C. and below; thus, such temperatures can beemployed to hydrolyzed the polysaccharide feed at a relatively slow ratewhen that result is desired.

The reaction should be continued for a period of time sufficient tohydrolyze at least a portion of the polysaccharide feed, and longerreaction times can be employed when complete hydrolysis is desired.Thus, when only nominal degree of hydration are desired (such as in theproduction of hydrated cellulose), short reaction times, relatively lowreaction temperatures, low urea-sulfuric acid concentrations, low waterconcentrations, and/or low surfactant concentrations can be employed toachieve that result. Most often, however, it is preferable to effecthydration of at least about 50 percent of the polysaccharide to itsconstituent monosaccharides, and, when the production of monosaccharidesis the essential object of the reaction, it is preferable to continuethe hydrolysis reaction until essentially all, i.e., 100 percent of thepolysaccharide, has been converted to monosaccharides. Accordingly, thehydrolysis reaction will usually be allowed to continue for at leastabout 1 minute, generally at least about 5 minutes, with most reactionsinvolving reaction times of about 5 minutes to about 100 hours. Reactiontimes of about 10 minutes to about 2 hours under otherwise moderateconditions, e.g., moderate temperatures of 20° to 60° C., are sufficientto effect complete hydrolysis of many polysaccharide sources such ascotton and other plant matter such as rice stubble, corn stubble, andthe like. For instance, 400 grams of cotton can be completely convertedto glucose in one hour at 25° C. by immersion in 500 grams of a 1/1/1molar ratio mixture of urea, sulfuric acid, and water, respectively,diluted with an additional 45 grams of water.

The hydrolysis reaction can be terminated, if desired, by diluting thereactant-polysaccharide mixture, separating the polysaccharide from theremaining reactants, and/or neutralizing the sulfuric acid reactant. Thereactant-polysaccharide mixture can be diluted with water and/or othersolvents or diluents to the point that the concentration of theurea-sulfuric acid component becomes very low with a consequentreduction in reaction rate. Separation of the polysaccharide from theremaining reactants can be effected by washing, or extracting thepolysaccharide from the reactants, or by crystalizing the urea-sulfuricacid component at low temperatures. Neutralization of the sulfuric acidcan be effected by the addition of any suitable organic or inorganicbase such as ammonia, sodium hydroxide, calcium hydroxide, amines, andthe like.

Following the completion of the reaction, the reactant mixturecontaining partially and/or completely hydrolyzed polysaccharide can beemployed as animal feed, or as a fermentation medium for the productionof fermentation products such as alcohols, or it can be separated toisolate monosaccharide and/or partially hydrolyzed polysaccharideproduct.

The reaction mixture containing partially or completely hydrolyzedpolysaccharides also contains urea and sulfuric acid and can be employeddirectly as feed for animals, such as ruminant mammals, which cantolerate the urea concentrations remaining in the composition (provided,of course, that the composition does not contain incompatible solventsor diluents). Optionally, the reactant composition can be neutralizedprior to feeding by the addition of stoichiometric or excess quantitiesof ammonia, sodium hydroxide, or non-toxic other organic or inorganicbases.

Reaction products which contain monosaccharides and/or partiallyhydrated polysaccharides also can be employed directly as fermentationmedia for the manufacture of alcohols and other fermentation products byknown enzymatic and/or bacterial processes. The fermentation product canbe neutralized prior to exposure to acid-sensitive bacteria or othercomponents of the fermentation media by the addition of appropriateorganic or inorganic bases such as ammonia, sodium hydroxide, magnesiumhydroxide, etc., some of which serve as nutrients for fermentationbacteria. The resulting alcohol product can be separated bydistillation, and the residue can be employed as a high nitrogenfertilizer or animal feed supplement.

Partially hydrolyzed polysaccharides (such as hydrated cellulose andpartially hydrolyzed sawdust, wood fibers, paper, and/or vegetablematter) which have not been sufficiently hydrated to become dissolved inthe reaction medium can be separated from the urea-sulfuric acidcomponent and other components of the reaction medium by conventionalphysical separation means such as filtration, centrifuging, decanting,and, optionally, can be further purified by washing with water or othersolvent.

Monosaccharides and/or lower molecular weight polysacchardies soluble inthe reaction medium (e.g., polysaccharides containing 2 to about 100saccharides units per molecule) can be recovered from the reactionmedium by procedures such as crystallization and/or solvent extraction.Such materials can be crystallized from relatively concentratedsolutions, e.g., solutions containing 10 weight percent solute or more,by reducing solution temperature to less than 20° C. or less than 0° C.or below. Crystallized material can be recovered by physical separationmeans such as filtration, centrifuging, and the like, and thesupernatant phase containing urea, sulfuric acid, water, and optionallyother solvents or diluents, can be recycled to the hydration reaction.

In the alternative, product monosaccharides and lower molecular weightpolysaccharides can be recovered by extraction with appropriate solventsincluding ethers such as tetrahydrofuran, diethyl ether, methylethylether, etc., and/or chlorinated hydrocarbons such as methyl chloride,trichloroethane, perchloroethane, carbon tetrachloride, etc. Recovery ofthe monosaccharide and/or lower molecular weight polysaccharide from theextraction solvent can be effected by conventional means such as lowtemperature crystallization or by solvent distillation.

The invention is further described by the following examples which areillustrative of specific modes of practicing the invention and are notintended as limiting the scope of the invention as defined by theappended claims.

EXAMPLE 1

400 grams of cotton fiber were immersed in 545 grams of a solutioncontaining 31.3 weight percent urea, 51.1 weight percent sulfuric acid,and 17.6 weight percent water, and the mixture was stirred at roomtemperature (about 23° C.) for one hour. The urea and sulfuric acid, incombination, constituted 82.4 weight percent of the solution and 47.5weight percent of the mixture of polysaccharide (cotton), urea, sulfuricacid, and water, and the relative proportions of urea and sulfuric acidcorresponded to a urea/sulfuric acid molar ratio of 1. During the onehour reaction period, the cotton "dissolved" to produce a colorlesssyrup. There was no evidence of significant heat or of any gasevolution, and titration of the product mixture with standard baseindicated that the final acid concentration was the same as the initialacid concentration. Thus, no acid consumption had occurred. Analyses ofthe product established that it was composed of glucose and the startingurea-sulfuric acid adduct.

EXAMPLE 2

Sawdust from which the lignins have been removed by liquid ammoniatreatment can be partially hydrolyzed by immersing 100 grams of thetreated sawdust in 500 grams of the urea-sulfuric acid-water solutiondescribed in Example 1 for 2 minutes at 50° C. The partially hydrolyzedsawdust then can be separated by filtration and further purified bywater washing.

EXAMPLE 3

Rice stubble can be converted to glucose by immersing 50 grams of finelyground rice stubble in 200 grams of an aqueous solution containing 20weight percent urea, 32 weight percent sulfuric acid, and 48 weightpercent water and agitating the resulting mixture at 40° C. for onehour.

Numerous variations and modifications of the concepts of this inventionwill be apparent to one skilled in the art in view of the aforegoingdisclosure and the appended claims and are intended to be encompassedwithin the scope of this invention defined by the following claims.

I claim:
 1. A composition comprising urea, sulfuric acid, water, and apolysaccharide in which the urea/sulfuric acid molar ratio is at leastabout 1/4 and less than 2, and wherein a sufficient proportion of saidurea and sulfuric acid is present as the monourea-sulfuric acid adductto hydrolyze said polysaccharide.
 2. The composition defined in claim 1wherein said urea/sulfuric acid molar ratio is about 1/2 to about 3/2,said urea and sulfuric acid, in combination, constitute at least about 1weight percent of said composition, and said polysaccharide constitutesat least about 1 weight percent of said composition.
 3. The compositiondefined in claim 1 wherein said urea/sulfuric acid molar ratio is atleast about 1/2, and said urea and said sulfuric acid, in combination,constitute at least about 10 weight percent of said composition.
 4. Thecomposition defined in claim 1 wherein said polysaccharide comprises amember selected from the group consisting of cellulose-containingmatter, plant and animal starches, and combinations thereof.
 5. Thecomposition defined in claim 3 wherein said polysaccharide comprises amember selected from the group consisting of cellulose-containingmatter, plant and animal starches, and combination thereof.
 6. Thecomposition defined in claim 1 which further comprises a solvent otherthan water.
 7. The composition defined in claim 6 which comprises lessthan about 1 weight percent water.
 8. The composition defined in claim 1which further comprises a surfactant.
 9. The composition defined inclaim 3 which further comprises a member selected from the groupconsisting of surfactants, solvents other than water, and combinationsthereof.
 10. The composition defined in claim 1 wherein said molar ratioof said urea to said sulfuric acid is at least about 1/2, said urea andsulfuric acid, in combination, constitute at least about 5 weightpercent of said composition, and said polysaccharide constitutes atleast about 5 weight percent of said composition.
 11. A compositioncomprising urea, sulfuric acid, water, and a polysaccharide in whichsaid urea and sulfuric acid, in combination, constitute at least about 5weight percent of said composition, said polysaccharide constitutes atleast about 5 weight percent of said composition, the molar ratio ofsaid urea to said sulfuric acid is at least about 1/4 and less than 2,and a sufficient proportion of said urea and sulfuric acid is present asthe monourea-sulfuric acid adduct to hydrolyze said polysaccharide. 12.The composition defined in claim 11 comprising a member selected fromthe group consisting of surfactants, solvents other than water, andcombinations thereof.
 13. The composition defined in claim 11 whereinsaid polysaccharide comprises a member selected from the groupconsisting of cellulose-containing matter, plant and animal starches,and combinations thereof.
 14. A composition of matter comprising urea,sulfuric acid, water, and a polysaccharide in which a sufficientproportion of said urea and said sulfuric acid is present as themonourea adduct of sulfuric acid to hydrolyze said polysaccharide, saidurea and sulfuric acid, in combination, being in a molar ratio betweenabout 1/1 and 3/2 and constituting at least about 5 weight percent ofsaid composition, and said polysaccharide constitutes at least about 5weight percent of said composition.
 15. The composition defined in claim14 wherein said water constitutes at least about 5 weight percent ofsaid composition.
 16. The composition defined in claim 14 comprising amember selected from the group consisting of surfactants, solvents otherthan water, and combinations thereof.
 17. The composition defined inclaim 14 wherein said polysaccharide comprises a member selected fromthe group consisting of cellulose-containing matter, plant and animalstarches, and combinations thereof.
 18. A composition comprising apolysaccharide and an amount of the monourea adduct of sulfuric acidsufficient to hydrolyze said polysaccharide in the presence of water,the molar ratio of urea to sulfuric acid forming said adduct beingbetween about 1/4 and 7/4.
 19. The composition defined in claim 18comprising a member selected from the group consisting of surfactants,solvents other than water, and combinations thereof.
 20. The compositiondefined in claim 18 wherein said polysaccharide comprises a memberselected from the group consisting of cellulose-containing matter, plantand animal starches, and combinations thereof.